How to Calculate the Number of Concrete Bags Required per Yard

Calculating how many bags of concrete you need for a one-yard or multi-yard pour is a common challenge on site. Whether you’re a contractor working a job, or a homeowner tackling a patio, getting the bag count right avoids running out mid-pour or wasting excess material. In this guide I’ll walk you through how to convert concrete volume into bag counts by the yard, include exact tables for popular bag sizes (40 lb, 50 lb, 60 lb, 80 lb and 20 kg bags), and show you how we bring field practice into the math.

Why Bags per Yard Matters

When concrete is specified by cubic yards (or cubic metres), you’ll often order by volume. But bagged concrete mixes are sold by weight or bag count—not by yard. To plan appropriately:

You need to know how many bags equate to one cubic yard of concrete.
You need an idea of how different bag sizes and yields change that count.
You need to allow for waste, spillage and placement variation (because on-site reality never matches perfect theory).

For example: one job I supervised had a 2-yard pour using 80 lb bags; we drafted count assuming 45 bags per yard, but due to form over-excavation and waste we used closer to 48 bags/yard. Having the right base number helped avoid a mid-pour scramble.

Step-by-Step / Formula Section

Here’s how you move from a cubic-yard target to bag count.

1. Know your base volume: one cubic yard

Remember that: 1 yd³ = 27 ft³

This is the standard conversion when working in feet. So when you see “per yard” you’re working off 27 cubic feet of concrete.

2. Determine yield per bag for your bag size

Manufacturers publish yield values. For example, one supplier shows:

40 lb bag yields ~0.30 ft³
50 lb bag yields ~0.375 ft³
60 lb bag yields ~0.45 ft³
80 lb bag yields ~0.60 ft³

3. Calculate bags per cubic yard

The formula is basically: Bags per yd³ = 1 yd³ ÷ (Yield per bag in yd³)

Or if you have yield in ft³: Bags per yd³ = 27 ft³ ÷ (Yield per bag in ft³)

For example, using 80 lb bag yield ~0.60 ft³: Bags per yd³ = 27 ÷ 0.60 ≈ 45 bags per yard

4. Multiply by number of yards and add contingency

Let’s say you need 3 yards:
Total Bags = Bags per yd³ × 3 yards

Then add an extra 5-10% for waste, irregular subgrades, hand mixing losses etc. Field practice always includes this margin.

Example Calculation

Let’s walk through a realistic example:

Project: Pouring 2.5 cubic yards of a slab using 60 lb bagged mix (yield ~0.45 ft³ each).
Step 1: Bags per yard (60 lb bags)
Bags per yd³ ≈ 27 ft³ ÷ 0.45 ft³ per bag = 60 bags per yard

Step 2: For 2.5 yards
2.5 × 60 = 150 bags

Step 3: Add contingency (say 8%)
150 × 1.08 ≈ 162 bags

So you’d order approximately 162 bags of 60 lb mix to cover 2.5 yards safely.

If instead you used an 80-lb bag:
Bags per yd³ ≈ 45 Total Bags ≈ 2.5 × 45 = 112.5 → round up to 113 With 8% extra → ~122 bags

You can see how bag size/ yield changes the count significantly.

Quick Reference Table — Bags per Cubic Yard

Bag Size	Approx Yield	Bags per Yard
40 lb	~0.30 ft³	~90 bags
50 lb	~0.375 ft³	~72 bags
60 lb	~0.45 ft³	~60 bags
80 lb	~0.60 ft³	~45 bags
20 kg (≈44 lb) *	Yield varies by brand	~100-110 bags (approx)

* The 20 kg bag (common outside US) requires checking manufacturer yield; approximate figure based on weight conversion and typical ratios.

Field note: Always round up to the next whole bag count, and present this table to crew or supplier as part of your specification.

Pro Tips / Field Notes

Check the yield label on the bag you’re using. The quoted yield (~0.45 ft³, ~0.60 ft³ etc) is based on the manufacturer’s mix design and may differ by region or brand.
Understand the job size: For very small jobs (less than 0.3 yd³) the “bags per yard” rule still helps, but waste-to-volume ratio increases—so ordering extra is even more important.
Subgrade and over-fill: If your form depth is deeper than design or base is uneven, you might need more volume than you calculated—adding the contingency helps mitigate this.
Mixing method matters: Hand mixing large numbers of bags increases losses compared to truck or machine mixing. Always build margin for real-site effects.
Bag size selection: Using 80 lb bags means fewer bags to handle (good for time) but heavier bags, more manpower or mechanical handling. 60 lb bags are often easier to move.
Communicate with the crew: Share the “bags per yard” number and your target count with your team so they understand the plan and can alert you if actual usage is trending off plan.
Use the right tool: For quick verification, plug your numbers into the Concrete Bags Calculator to cross-check your manual estimates.

Understanding Concrete Bag Coverage and Yield
Convert Concrete Volume Into Bags
Reference Guide — Calculating Bags of Concrete for Any Project
Visit Concrete Calculator Max for full tools, calculators and support.

Conclusion

Knowing how many bags of concrete you need per yard helps you move from volume-spec to bag-order with confidence. Use the yield numbers, apply the bags-per-yard table, add your contingency for site realities—and you’ll stand by your numbers. That means fewer surprises on site, fewer wasted bags, and smoother pours.

You can double-check your math anytime with the Concrete Bags Calculator — it saves time, errors, and guesswork on site.